Have read some of the other posts but not seen exactly this issue. My son's 240 has about 170k on it. Most of the old rubber and plastic has been replaced with silicone tubing. Was tuned with new plugs, wires and distributor about 2 years ago, but he doesn't drive it a lot. (Helga is his first car and will probably stay with him for life!!!)
After the engine warms up, at idle either in park or stopped in drive, it has what I'd call a stutter. Runs smooth for about 3 seconds, then a brief shudder like it's missing, then smooths again for about 3 seconds, then the shudder. It's pretty regular and is only at idle. I sped up the idle a bit and it's not as pronounced, but it's still there. We cleaned the AMM, the distributor, the plugs, and I sprayed some cleaner around with the engine idling to see if it smoothed out, but nothing happened. There are no codes...just good ol' 1-1-1.
I still think there's a leak somewhere but I sure haven't located it. Runs fine at speed, just has this rough idle. Does not surge, just has the slight shudder. Doesn't die. It's just irritating, made even worse when I can't find something to fix. Any ideas would be greatly appreciated.
Thanks
Scott